With little efforts, to estimate the appropriateness of automatic defect classification, and to make classification criteria settable with a guarantee for the better classification performance, defects unknown with their classification classes are classified based on two different classification criteria. Also, defects differed in classification results are collected, and each thereto, a defect classification class is provided by using a manual. Then, the defects provided with the classification classes are divided into two types of groups: one is a setting group for the classification criteria; and the other is an evaluation group. Based on the classification criteria that is so set as to classify the defects included in the setting group with the maximum performance, the classification performance of a case where classification is applied to defects included in the evaluation group is calculated, and the appropriateness of thus set classification criteria is evaluated.